Control device for a reciprocating machine

ABSTRACT

A control device for distributing a source of compressed fluid to a chamber housing a reciprocating member, the device including a valve means connecting the source of compressed fluid to the chamber and being switchable between two operating modes in which compressed fluid is introduced into said chamber to the respective ends of said reciprocating member to cause the latter to reciprocate in said chamber. The valve is normally in one of the modes and is switchable to, and maintained in, the other mode in response to a predetermined pressure existing in the chamber.

United States Patent Schmidlin [54] CONTROL DEVICE FOR A RECIPROCATING MACHINE [72] Inventor: Albertus E. Schmidlin, Caldwell,

[73] Assignee: TPI & Cornpany, Montclair, NJ.

[22] Filed: Dec. 4, 1969 [21] Appl. No.: 881,994

[52] US. Cl. ..91/3, 91/317, 91/325 [51] Int. Cl ..F01l25/06 [58] Field of Search ....91/317, 290, 307, 3; 137/815 [56] Reierences Cited I UNITED STATES PATENTS 3,107,850 10/1963 Warren et all ..137/81.5 3,565,186 2/1971 Bilodeay ..91/3 2,609,792 9/1952 OFarrell ..91/317 3,124,999 3/1964 Woodward ..91/290 3,245,483 4/1966 Etzkorn ..91/317 51 Oct. 10,1972

3,340,896 9/ 1967 Mon et al. ..91/307 3,396,631 8/1968 Woodward ..91/290 3,516,763 6/1970 Monton ..91/3

Primary Examiner-Paul E. Maslousky Attorney-S. A. Giarratana [57] ABSTRACT A control device for distributing a source of compressed fluid to a chamber housing a reciprocating member, the device including a valve means connecting the source of compressed fluid to the chamber and being switchable between two operating modes in which compressed fluid is introduced into said chamber to the respective ends of said reciprocating member to cause the latter to reciprocate in said chamber. The valve is normally in one of the modes and is switchable to, and maintained in, the other mode in response to a predetermined pressure existing in the chamber.

13 Claims, 2 Drawing Figures PATENTEDBBI 10 I912 3.696.709

FIGZ.

22 INVENTOR ALBERTUS E. SCHMIDLI N i -czmb m mmgww 28 24 I ORNEY' CONTROL DEVICE FOR A RECIPROCATING MACHINE BACKGROUND OF THE INVENTION This invention relates to a control device for a reciprocating machine and, more particularly, to such a device utilizing a fluidic valve.

The use of fluidic valving in numerous applications has demonstrated its advantages over conventional devices. The major features which attribute to this are its ruggedness, its reliability, and its low cost. In addition, fluidic valving enjoys a relative high resistance to hostile environments such as high temperature, explosive atmospheres, magnetic fields, etc., an absence of electrical currents and field of any sort, and a simplicity of integration.

These features are possible because of the static nature of the device. The absence of moving parts eliminates problems with sliding surfaces and bearings, impact loads which are present in dynamic machinery, and costly manufacturing processes which are inherent in moving parts. These features can be exploited to a major'degree where the primary function of the device is to control fluid flow. However, when the primary function requires the control of dynamic machinery, then the application is not quite so straightforward. The integration of the purely fluidic elements with the moving parts of the mechanismmust be accomplished with due consideration of the salient features of both types of functional design.

The use ofa fluidic valve to control a reciprocating machine such as a demolition tool is a prime example of this problem: The purpose of the demo tool is to provide a number of repetitive blows to an anvil in order to accomplish mechanical work. The fluidic control must not only drive the piston in a cyclic manner, up and down, but must do so in an efficient manner. That is, it must drive the piston downward so that the hammer strikes the anvil with an impact which represents a major portion of the input power, and it must return the piston to the top of the stroke without physical contact and impact which would shorten the life of the device. Therefore the functional timing of the control device is important, and the inter-relationship of these characteristics with the other inherent features of an impact demolition too] must be carefully considered in order to arrive at an efficient design.

Some proposals have been tried for controlling the cyclic motion of a piston using fluid power and a fluidic control. However, these proposals fail to derive maximum output from the fluid source since they create excessive impedance during the power stroke as a result of returning the piston to the top of its return stroke.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a control device of the above type which derives maximum power from its fluid source by eliminating excessive impedance during the power stroke of the reciprocating machine.

Toward the fulfillment of this object the control device of the present invention comprises a valve means connecting'a source of compressed fluid to an operating chamber for a reciprocating member, said valve means being switchable between a first and second modein which compressed fluid is introduced into said chamber to the respective ends of said reciprocating member to cause the latter to reciprocate in one of said chambers, said valve normally being in one of the modes and being switchable to, and maintained in, the other mode in response to a predetermined pressure existing in said chamber.

BRIEF DESCRIPTION OF THE DRAWINGS Reference is now made to the accompanying drawings for a better understanding of the nature and objects of the present invention. The drawings illustrate the best mode presently contemplated for carrying out the objects of the invention and are not to be construed as restrictions or limitations on its scope. In the drawings:

FIG. 1 is a cross-sectional view of the control device of the present invention; and

FIG. 2 is an enlarged cross-sectional view of the fluidic valve utilized in the device of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, thereferenee numeral 10 refers to the control device of the present invention which is adapted to be operatively connected to a reciprocating device which, for the purposes of example, may be in the form of a demolition tool, whereby the control device 10 is adapted to reciprocally drive a piston 12 to provide a series of repetitive blows to an anvil to accomplish mechanical work, in a known manner.

Toward this end, the piston 12 is mounted for reciprocating movement within a tool housing 14, and is adapted to be actuated by compressed air, or other fluid, passing from a source (not shown) into the housing 14 via a tubing 16, and a spring loaded, manually operated valve 18.

A fluidic valve 20, in the form of a monostable fluidic power amplifier, has a supply port 22, a control port 24, and two output ports 26 and 28. Control port 24 and output port 28 open at bottom surface 29.

The supply port 22 is adapted to communicate with the tubing 16 upon actuation of the valve 18. The output port 26 registers with a longitudinal passage 30, which, in turn, registers with an enlarged longitudinal passage 32 communicating with an operating chamber 34 for the piston 12 via a port 36.

The output port 28 and the control port 24 both open at the bottom surface 29 directly into the upper portion of the chamber 34.- By directly is meant that there is no passage in the housing located intermediate the valve means 20 and the chamber 34. The design of the valve 20 is such that, in the absence of a control signal in the form of air pressure at the control port 24, the air flow through the amplifier is via the output port 26, while, when a positive air pressure exists at the control port 24, the flow through the amplifier is diverted to the output port 28.

An additional port 38 is provided through a wall of the housing 14 and connects the chamber 34 to atmosphere.

The valve functions as follows. Assuming the piston 12 to be in its Iowerrnost position as viewed in FIG. 1, which is at the bottom of its power stroke, compressed fluid is admitted to the device by manually depressing the handle of the valve 18, which admits the air from the source to the supply port 22 of the amplifier 20. Since there is no positive pressure at the control port 24, the air flows out of the output port 26, through the passages 30 and 32 and into the bottom portion of the chamber 34. This air builds up a pressure under the piston 12, thereby urging it upward untilit covers the port 38, thereby trapping atmospheric air in the portion of the chamber 34 above the piston, which air is compressed as the piston continues its upward travel.

Compressed fluid continues to flow into the lower part of the cylinder in the above manner causing the piston to continue its upward movement. As a result of further movement, the exhaust port 38 is uncovered and the exhausting process of the portion of the chamber below the piston begins while the piston continues to move upward under the momentum it gained in its earlier movement. Meanwhile, the air which is trapped above the piston is still being compressed until a pressure is created above the piston which forces air through the control port 24 and serves to switch the flow of compressed air through the amplifier to the output port 28. The residual air above the piston is sufficient to damp the remaining upward motion of the piston and to start it on its downward power stroke. Immediately after this, the compressed fluid passing through the output port 28 acts on the upper surface of the piston 12 and supplies the necessary force to effect the power stroke, during which time the pressure in the portion of the chamber above the piston is sufficient to hold the fluidic amplifier in the latter position via the control port 24.

As the piston moves down a sufficient distance to pass and uncover the exhaust port 38, the compressed air in the upper portion of the chamber exhausts very suddenly because of the sudden opening of the latter port. This allows explosive venting of the air and, in fact, permits the instantaneous pressure at the control port 24 to become substmospheric. This condition negates the control pressure which was needed to hold the fluidic amplifier in the power position and, in addition, applies a refraction wave to the control port 24. As a result, the amplifier is sucked back to its initial state, and flow through the amplifier is thus switched to the output port 26, thereby starting the return stroke and the beginning of the second cycle.

Thus, with the foregoing, maximum power is derived from the air source without creating any unnecessary impedance to piston movement.

Of course, other variations of the specific construction and arrangement of the control devices disclosed above can be made by those skilled in the art without departing from the invention as defined in the appended claims.

l claim:

I. A gas operated demolition tool comprising a housing with a hollow chamber therein, a reciprocating member located within said chamber for delivering blows to an anvil at the bottom of said chamber, monostable fluidic power amplifier valve means located within in the tool housing adjacent to the upper portion of said chamber, said valve means having a bottom surface in direct communication with said chamber, said valve means having an input port and first and second output ports and a control port, said second output port and said control port located at said bottom surface of said valve means and opening directly into said hollow chamber of said housing, said first output port of said valve means communicating with said hollow chamber of said housing near the lower end thereof through a passage in the tool housing, means on said tool for connecting said input port to a source of compressed gas, said valve means being operable to cause said reciprocating member to reciprocate in said chamber, said valve means normally directing the gas to said first output port and being switchable by means of said control port to direct the gas to said second output port in response to a predetermined pressure existing in said chamber.

2. The tool of claim 1 further comprising means to establish and relieve said pressure in response to said reciprocating member attaining predetermined positions relative to said chamber.

3. The tool of claim 1 further comprising means to selectively admit additional gas into said chamber, which additional gas is compressed during movement of said reciprocating member in one direction to establish said predetermined pressure in said chamber and damp the final portion of said latter movement.

4. The tool of claim 3 wherein said means to selectively admit additional gas into said chamber comprises a port connecting said chamber to atmosphere, said port adapted to be covered and uncovered by said reciprocating member.

5. The tool of claim 3 wherein said predetermined pressure is maintained in said chamber during a portion of the movement of said reciprocating member in the other direction, and further comprising means to vent said chamber to relieve said predetermined pressure after said latter portion of movement.

6. The tool of claim 5 wherein said means to vent said chamber is also adapted to vent said chamber during movement of said reciprocating member in said one direction.

7. The tool of claim 5 wherein said means to vent said chamber comprises a port connecting said chamber to atmosphere, said port adapted to be covered and uncovered by said reciprocating member.

8. The tool of claim 6 wherein movement of said reciprocating member in said one direction corresponds to its return stroke, and wherein movement of said reciprocating member in said other direction corresponds to its power stroke.

9. A gas operated tool having a reciprocating member within a chamber in the tool for delivering blows to an anvil at the bottom of said chamber, a housing surrounding and defining said chamber, monostable power amplifier valve means located within the tool adjacent to the upper portion of said chamber, said valve means having a bottom surface in direct communication with said chamber, said valve means having an input port and first and second output ports and a control port, said second output port and said control port located at said bottom surface of said valve means and opening directly into said chamber in said housing, said first output port of said valve means communicating with said chamber near the lower end thereof through a passage in said housing, means on said tool for connecting said input port to a source of compressed gas, said valve means being operable to cause said reciprocating member to reciprocate in said chamber; and means responsive to said reciprocating member attaining at least one predetermined position in said chamber for venting said gas from said chamber, said valve means switching the path of the gas flow from one output port to the other in response to the venting os said gas from said chamber.

10. The tool of claim 9 wherein said means for venting said gas from said chamber is adapted to vent said gas during movement of said reciprocating member in both directions.

11. The tool of claim 9 further comprising means to selectively admit additional gas into said chamber, which additional gas is compressed during movement of said reciprocating member in one direction to establish said predetermined pressure in said chamber and damp the final portion of said latter movement.

12. The tool of claim 11 wherein said means for venting said gas from said chamber is also adapted to vent said additional gas from said chamber.

13. The tool of claim 9 wherein said means for venting said gas from said chamber comprises a port connecting said chamber to atmosphere, said port adapted to be covered and uncovered by said reciprocating member. 

1. A gas operated demolition tool comprising a housing with a hollow chamber therein, a reciprocating member located within said chamber for delivering blows to an anvil at the bottom of said chamber, monostable fluidic power amplifier valve means located within in the tool housing adjacent to the upper portion of said chamber, said valve means having a bottom surface in direct communication with said chamber, said valve means having an input port and first and second output ports and a control port, said second output port and said control port located at said bottom surface of said valve means and opening directly into said hollow chamber of said housing, said first output port of said valve means communicating with said hollow chamber of said housing near the lower end thereof through a passage in the tool housing, means on said tool for connecting said input port to a source of compressed gas, said valve means being operable to cause said reciprocating member to reciprocate in said chamber, said valve means normally directing the gas to said first output port and being switchable by means of said control port to direct the gas to said second output port in response to a predetermined pressure existing in said chamber.
 2. The tool of claim 1 further comprising means to establish and relieve said pressure in response to said reciprocating member attaining predetermined positions relative to said chamber.
 3. The tool of claim 1 further comprising means to selectively admit additional gas into said chamber, which additional gas is compressed during movement of said reciprocating member in one direction to establish said predetermined pressure in said chamber and damp thE final portion of said latter movement.
 4. The tool of claim 3 wherein said means to selectively admit additional gas into said chamber comprises a port connecting said chamber to atmosphere, said port adapted to be covered and uncovered by said reciprocating member.
 5. The tool of claim 3 wherein said predetermined pressure is maintained in said chamber during a portion of the movement of said reciprocating member in the other direction, and further comprising means to vent said chamber to relieve said predetermined pressure after said latter portion of movement.
 6. The tool of claim 5 wherein said means to vent said chamber is also adapted to vent said chamber during movement of said reciprocating member in said one direction.
 7. The tool of claim 5 wherein said means to vent said chamber comprises a port connecting said chamber to atmosphere, said port adapted to be covered and uncovered by said reciprocating member.
 8. The tool of claim 6 wherein movement of said reciprocating member in said one direction corresponds to its return stroke, and wherein movement of said reciprocating member in said other direction corresponds to its power stroke.
 9. A gas operated tool having a reciprocating member within a chamber in the tool for delivering blows to an anvil at the bottom of said chamber, a housing surrounding and defining said chamber, monostable power amplifier valve means located within the tool adjacent to the upper portion of said chamber, said valve means having a bottom surface in direct communication with said chamber, said valve means having an input port and first and second output ports and a control port, said second output port and said control port located at said bottom surface of said valve means and opening directly into said chamber in said housing, said first output port of said valve means communicating with said chamber near the lower end thereof through a passage in said housing, means on said tool for connecting said input port to a source of compressed gas, said valve means being operable to cause said reciprocating member to reciprocate in said chamber; and means responsive to said reciprocating member attaining at least one predetermined position in said chamber for venting said gas from said chamber, said valve means switching the path of the gas flow from one output port to the other in response to the venting os said gas from said chamber.
 10. The tool of claim 9 wherein said means for venting said gas from said chamber is adapted to vent said gas during movement of said reciprocating member in both directions.
 11. The tool of claim 9 further comprising means to selectively admit additional gas into said chamber, which additional gas is compressed during movement of said reciprocating member in one direction to establish said predetermined pressure in said chamber and damp the final portion of said latter movement.
 12. The tool of claim 11 wherein said means for venting said gas from said chamber is also adapted to vent said additional gas from said chamber.
 13. The tool of claim 9 wherein said means for venting said gas from said chamber comprises a port connecting said chamber to atmosphere, said port adapted to be covered and uncovered by said reciprocating member. 